Method and apparatus for suppressing the noise of an aircraft jet engine

ABSTRACT

An aircraft jet engine is provided with a semicylindrical reflector/suppressor shield which for takeoff of the aircraft is extended sufficiently downstream of the engine nozzle to intercept the accompanying cone of noise of the jetstream several nozzle diameters aft of the nozzle in the region of the expansion boundary of the jetstream where the noise level is maximum so that such noise which otherwise would be radiated toward the ground is reflected by the shield to thus substantially reduce the effective perceived noise level at the ground. The shield is interrelated structurally and functionally with the engine and nozzle structures so that appropriately configured nozzle and nozzle adjuncts effect stream division, mixing and frequency conversion, ejector action for thrust augmentation at takeoff, and thrust reversal for aircraft braking on landing, all rendered compatible with the operation of the reflector/suppressor shield and the noise abatement provided thereby.

United States Patent 72 Inventor Burt F. Haynes 3,262,264 7/1966Gardiner et al 239/1273 Chula Vista, Calif. 3,495,682 2/1970 Treiber181/3322] [21] Appl. No. 58,282 3,516,511 6/1970 Urquhart 181/3322] [22]Filed July 27, [45] Patented Nov. 23, 1971 [73] Assignee RohrCorporafion 1,436,412 3/1966 France 181133.221

Chula Vista, Calif. Primary Examiner- Robert S. Ward, Jr.

Attorney-George E. Pearson [54] METHOD AND APPARATUS FOR SUPPRESSING THENOISE OF AN AIRCRAFT JET ENGINE ABSTRACT: An aircraft jet engine isprovided with a 22 Claims, 7 Drawing Figs. semicylindrical reflector/supressor shield which for takeoff P [52] Us cl 18] [33E of the aircraftis extended sufficiently downstream of the en 239/265 gine nozzle tointercept the accompanying cone of noise of the [51] in CI 33/66jetstream several nozzle diameters aft of the nozzle in the re- 8 FolnIn; gion of the expansion boundary of the jetstream where the [so]Fieldofsearch 181/43 51 noise level is maximum so that such noise whichotherwise 05 33 I would be radiated toward the ground is reflected bythe shield 239N273 265'] l, 261 l 3' 265.17, 265-19 it:t1111:;ls(\)1ll:;tdantlally reduce the effective perceived 110156 levelThe shield is interrelated structurally and functionally with the [56]Referemes cu engine and nozzle structures so that appropriatelyconfigured UNITED STATES PATENTS nozzle and nozzle ad uncts effectstream dIVlSlOll, mixing and frequency conversion, ejector action forthrust augmentation 2'83989] 6/1958 Drakeley 239/26533 at takeoff, andthrust reversal for aircraft braking on landing, $027,710 4/1962 Maymer181/3322] all rendered compatible with the operation of the reflec-3'084'507 4/1963 Kle'rfhans 17153-222 tor/suppressor shield and thenoise abatement provided 3,174,282 3/1965 Harrison l81/33.221 thereby 24n :3 f 3 I r.r::m .L 1 s Lg 22-5 |O 33-" I15? '71 r r" 36- 3 -37 3PATENTEDNOV 23 I97! SHEET 2 [If 2 INVIZNTOR.

BUR F. RAYNES ATTORNEY BACKGROUND OF THE INVENTION It is known that muchof the noise associated with the operation of a jet engine arises fromthe exhaust jet as the high-velocity, high-temperature gases shearthrough the surrounding air in the region of the expansion boundary ofthe jet stream. According to Murray and Gahagan, Great Britain, Pat. No.553,544, May 1951, the maximum level of the noise accompanying the jetstream arises in a hollow cone of about 80 to 120 included anglesurrounding the jet axis, and this noise radiates in all directionstransversely of the jet axis.

Murray and Gahagan theorized that the sound waves are refracted at theexit nozzle due to the difference in density between the hot gas andsurrounding cool air, and that the sound waves will not be refractedunless there is cold air surrounding the hot gas. Murray and Gahaganaccordingly discovered that a sound baffle structure for absorbingand/or reflecting sound waves, when spaced from the exit nozzle of thejet to provide a layer of cool air therebetween, gave rise to suchrefraction to thus direct the sound waves towards the baffle. They foundthat the baffle, moreover, when positioned with its leading edge at orslightly rearwardly of the nozzle exit plane and disposed to cut throughthe hollow cone to intercept the sound waves in the region of maximumnoise level, provided the maximum effect in shielding the fuselageaccommodation of an aircraft from noise which otherwise would beradiated thereto from the jet stream, the noise level being materiallyreduced by use of the baffle. The length of the baffle was selected soas to shield that length of the fuselage in which the noise level wouldotherwise be excessive.

It is known to corrugate the nozzle and/or its surrounding nacelle orcowling and to mix air with the hot gases issuing from the nozzle toaugment the thrust as well as to effect sound reduction through cooling,and also be division of the air and gas streams, to raise the frequencyof the accompanying noise. The high frequency content of the noiseattenuates rapidly, but the lowfrequency content, the maximum noiselevel of which arises several nozzle diameters downstream of the nozzle,radiates to the ground at objectionably high effective perceived noiselevel thereat.

SUMMARY OF THE INVENTION The present invention relates to methods andapparatus for suppressing the noise of an aircraft jet engine tosubstantially reduce the effective perceived noise level produced at theground during takeoff of the aircraft. This is accomplished by use of asemicylindrical reflector/suppressor shield which is extended into theregion of the expansion boundary of the jetstream to intercept theaccompanying cone of noise several nozzle diameters aft of the nozzle.

In accordance with one embodiment, the shield is formed as a removableportion of the cowling or nacelle surrounding the engine and its nozzle.In this sense it may serve as an access panel, making an enlarged areaof the exposed engine accessible for servicing. During takeoff, theshield is moved out of its stowed position around the engine andtranslated to its deployed position downstream of the nozzle.

In accordance with another embodiment, the reflector/suppressor is madethe terminal extension of a translatable ejector ring or barrel, thecombined length of the ejector and reflector in deployed position beingefiectively that of the reflector/suppressor of the first mentionedembodiment so that in this case, as in the first'embodiment, thereflector/suppressor intercepts the cone of noise by several nozzlediameters aft of the nozzle. The ejector thus serves to position thereflector for maximum noise reflection and absorption as well as toinject cooling air for sound suppression and thrust augmentation.

In the case of each embodiment, provision is made for mixing air withthe exhaust gases and for dividing the issuing jet streams to effectcooling and frequency conversion and resultant sound suppression of theaccompanying noise. In the case of each embodiment, moreover, provisionis made for accommodating reverser doors to be deployed during landingto effect braking of the aircraft.

The foregoing and additional features of the present invention willbecome more clearly apparent from the following detailed description ofthe best mode thus far devised for practicing the principles of theinvention, reference being had to the accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view in elevation of anaircraft jet engine showing its reflector/suppressor shield in deployedposition for takeoff of the aircraft;

FIG. 2 is a view similar to that of FIG. 1 but showing thereflector/suppressor shield in stowed position and the thrust reverserdoors in deployed position for braking of the aircraft on landing;

FIG. 3 is an end view of the nozzle and its fairing and of the shield asviewed along the line 3-3 of FIG. 1;

FIG. 4 is a view in elevation of an aircraft engine and its suppressorarrangement wherein a translatable ejector-reverser barrel and thereflector/suppressor shield translatably carried thereby are shown instowed position for inflight operation of the aircraft;

FIG. 5 is a view in elevation of the engine-suppressor arrangement ofFIG. 4 showing the ejector-reverser barrel and reflector/suppressorshield in deployed position for takeoff, as shown, or for landing asdepicted by the dashed line showing of the reverser doors;

FIG. 6 is a fragmentary end view as seen along the line 6-6 of FIG. 4;and

FIG. 7 is a sectional view of the sidewall reverser barrel shown inFIGS. 4 and 5.

DETAILED DESCRIPTION Referring now to the drawings for a more completeunderstanding of the invention and first more particularly to FIGS. 1 to3 thereof there is shown thereon a first embodiment of the invention inwhich a reflector/suppressor shield 10, which is generally ofsemicylindrical configuration and tapered somewhat rearwardly, is carvedout of and forms a separable part of the cowling 11 for housing orenclosing the fan engine 12. Although a fan engine is disclosed, it willbe understood that the principles and features of the invention may beembodied in a so called primary jet" type engine in which thereflector/suppressor shield would similarly be carved out of the nacelleor other housing surrounding the engine and its nozzle.

In the arrangement disclosed, the engine 12 is shown supported as by thepylon structure 13 from the aircraft wing 14 but, again, the scope ofthe invention in the application of the principles and features thereoftranscends any specific engine design or mounting arrangement therefor.It will be understood, moreover, that whereas for simplicity ofdisclosure, only one engine is shown, that in practice, an aircraftemploying the sound suppressor apparatus herein disclosed and claimedwill normally employ a plurality of such engines, each so equipped forsound suppression of the noise accompanying the jet stream issuing fromits nozzle.

The end portion of the engine nozzle 15 is corrugated to provide aso-called daisy" type of configuration 16, FIG. 3, to produce a divisionof the jet stream which issues from the nozzle, thereby to increase thehigh frequency content of the noise accompanying the stream. The depthof the corrugations increases from a point upstream of the end of thenozzle, as best depicted by the dashed line 17 in FIG. 1, to the maximumdepth at the end of the nozzle as depicted by the daisy configuration inFIG. 3. The corrugations in the nozzle are also depicted by the slidlines 18in FIG. 2.

The corrugated end portion of nozzle 15 is enclosed by a fairingstructure 20 which is combination ejector barrel and thrust reverser,sometimes referred to herein as an ejectorof the ejectorreverser barrel.Fairing 20 comprises a ring 21 which surrounds the nozzle so as toprovide a space therebetween for entrainment of slipstream air in acustomary ejector action. A pair of stangs 22, 23 extend rearwardly fromring 21 and are suitably supported on the nozzle 15. A pair of thrustreverser doors 24, 25 of substantially semicylindrical shape, whendisposed in the stowed position thereof, as shown in FIG. 1, bear attheir forward end surfaces against the rear end surface of ring 21 inclosing relation therewith, and along their longitudinal edge surfaces,bear against the stangs 22,23 in closing relation therewith.

As best seen in FIG. 2, the reverser doors are suitably movably mountedon the stangs 22, 23 as by a so-called 4-bar linkage" arrangementoflinks 26, 27, a set of4 links being employed, on each side of thenozzle in operative association with the stang mounted on that side.Enclosed within each stang is a bogie mechanism (not shown) foractuating the links to translate the doors between their respectivestowed and deployed positions of FIGS. 1 and 2. Such a bogie mechanismsuitable for the purpose is disclosed in detail in the copendingapplication of Felix Hom et al. for Jet Reverser Drive System, Ser. No.681,790, filed Nov. 9, 1967, assigned to the assignee of the instantapplication, and the disclosure of that case is incorporated herein byreference.

It will be noted that the downstream end surfaces 28 of doors 24, 25 areslanted inwardly and forwardly so that when these surfaces meet as shownin FIG. 2, the doors are slanted forwardly at an angle of about 10. Thedoors in this position are thus disposed substantially transversely ofthe jet axis and effectively block the jetstream in a spoiler action,directing it laterally with only a slight forward vector. The doors,however, have end plate structures depicted by the dashed lines 29 whichdirect the deflected jetstream forwardly of the engine.

The reverser doors are also corrugated as depicted at 31 in FIG. 3 andby the solid lines 32 in FIG. 2. When the doors are in their stowedposition of FIG. I wherein the shield is deployed for takeoff, thecorrugations in the nozzle and in the surrounding doors promote divisionof the jet and air streams respectively passed thereby to promote mixingand resultant sound suppression and thrust augmentation during takeoff.In the inflight condition, when the reverser doors have been translatedto their stowed position from the deployed position of FIG. 2, the airdrawn through the ejector barrel reduces base drag which would otherwiseoccur in the absence of an aspirating fairing for the corrugated nozzle.

The aforedescribed ejector barrel and reverser door arrangement isgenerally similar to that disclosed in the copending application of JackH. Hilbig for Method and Apparatus for Augmenting and Reversing Thrustand Reducing Base Drag and Noise of an Aircraft .let Engine, Ser. No.824,414, May 14, 1969, assigned to the assignee of the instantapplication, and the disclosure of that case is incorporated byreference herein.

It will be seen in FIG. I that with the shield 10 removed from housing11, that a large area of the engine 12 is exposed to thus render theengine easily accessible for servicing. The primary function of theshield, however, in making the same separable from the main housing 11,is to make the shield available for extension downstream of the nozzleto reflect and substantially suppress noise which otherwise would beradiated from the sides of the issuing jet stream and toward the groundduring takeoff and thus received, in the absence of the shield, withobjectional intensity in the airport and surrounding areas.

The normal divergence of the jet stream in issuing from nozzle isdepicted by the dash-dot line 34, this being sometimes referred to asthe expansion boundary of the jet stream which, for the nozzle structuredisclosed in the instant case, has a divergence angle of the order of 5relative to the jet axis 33. According to the investigations and theoryof Murray and Gahagan, aforementioned, the maximum noise level in thevicinity of an exhaust jet of a gas turbine engine arises in a hollowcone of about to included angle surrounding the jet axis, this includedangle being depicted by the dash-dot lines 35 in FIG. 1. Accordingfurther to the teachings of Murray et al., the baffle shield to havemaximum effect must cut through the hollow cone to intercept the soundwaves in the region of maximum noise level.

In accordance with more recent theories and actual tests, however, thenoise which causes the objectionable effective perceived noise levels atthe ground arises from the jet stream several nozzle diameters aft ofthe exit plane of the nozzle, thus indicating that the cone of noise ismore accurately delineated by the expansion boundary line 34. Thesetests and theories tend to clearly establish, moreover, that for maximumeffectiveness of the shield 10, it should extend into the region of theexpansion boundary of the jet stream several nozzle diameters aft of thenozzle, as shown, and preferably, at its downstream end portion, tointercept the expansion boundary, as shown, so that a phenomenon knownas attachment" occurs. According to this phenomenon, as tests haveproven, when the jet stream moves to engage the shield surface at theend portion of the shield, to thus attach to the shield, the attachmentprogresses upstream until all of the inner surface of the shield isengaged by the jet stream.

The reflector/suppressor of the instant invention was tested on a%-SC3.I8 model of a turbofan engine having an extended conical fannozzle with a primary mixer, and the noise from the nozzle was measuredwith and without the suppressor shield in place. For purposes of thetest, the reflector/suppressor shield consisted of a half shell bafilewhich was placed around one side of the nozzle. Two lengths of thebaffle were used for the tests, the two lengths being equivalent tothree and six diameters of the extended fan nozzle under test. Noisedata were recorded at five power settings covering the normal operatingrange of the engine under test, and the noise suppression valves werecalculated by plotting the maximum effective perceived noise level on aZOO-foot sideline for both tests. The difi erences in the data derivedwith and without use of the reflector/suppressor shield at constantenergy value provided the measure of effectiveness of the device as anoise suppressor. At a nozzle energy equivalent to takeoff thrustobtainable from the type of engine under test, the 6-nozzlediameterreflector/suppressor baffle provided 6.2 EPNdb. suppression (6.2 db.reduction in effective perceived noise level) and the 3-nozzle-diameterbaffle provided 3.4 EPNdb. suppression.

In the reflector/suppressor arrangement disclosed in FIGS. 1 to 3, theshield 10 has a length equal approximately to 4 times the effectivediameter of nozzle 15, that is, a length of 4- nozzle diameters.

The dash-dot lines 36 in FIG. 1 depict the swinging movements of theends of shield 10 to move the same in and out of the cowling 11, and thedash-dot lines 37 depict the translational movement involved intranslating the shield from such intermediate position downstream to thedeployed position of the shield, as shown, or upstream to itsintennediate position for swinging movement back into the cowling, whereit would occupy the position as shown in FIG. 2. The dash-dot lines 36and 37 also represent schematically the mechanism required for suchswinging and translating movements, such mechanism being of any suitabletype.

Referring now to FIGS. 4 to 7, there is shown thereon another embodimentof the reflector/suppressor of the instant invention wherein atranslatable ejector-reverser barrel 20, is interposed between thenozzle 15 and the reflector/suppressor shield 10 in its deployedposition of FIG. 5. Shield 10' for the purposes of this arrangement isapproximately half the length of the reflector/suppressor shield 10 ofFIGS. 1 to 3. Its downstream end, however, in the deployed position ofFIG. 5,

is as many nozzle diameters aft of the nozzle exit plane as thedownstream end of shield 10 in its deployed position of FIG. I.

It will be understood that the two embodiments of FIGS. 1 to 3 and FIGS.4 to 7, respectively, are generally similar and that the same referencecharacters are employed throughout the several views to designate thesame or similar elements of structure.

The ejector-reverser barrel 20, for example, is generally similaraforementioned the ejector-reverser barrel 20 of FIGS. 3. In the case ofejector-reverser barrel 20', the same comprises an upstream ring 21 andrearwardly extending therefrom a pair of diametrically opposed stangs,only one of which is shown in FIG. 6, this being stang 22'. The stangsand ring 21 have interfit therewith the reverser doors 24 and 25' which,in this case are pivotally supported on the stangs which have associatedwith the doors appropriate links, pivots and bogie drives, all asdisclosed in the aforementioned copending application, Ser. No. 681,790,of Hom et al., and the disclosure of that case is incorporated herein byreference thereto.

The stangs respectively are supported by a pair of elongated beams ortracks, one track 41 of which is best disclosed in FIG. 6 in attachedrelation to stang 22. Each track has inner and outer channels 42 and 43,respectively, of dovetail cross section, FIG. 6. Inner dovetail channel42 has slidably received therewithin an appropriately cross sectionallyshaped elongated beam or rail 44 which at its forward end isappropriately supported by the engine 12 preferably inside the cowling11', the diametrically opposite counterpart of rail 44 being similarlysupported on the other side of the engine. Also supported on the engineis a suitable drive motor 45 having a drive element such as a gear 46disposed in operative driving engagement with a gear rack 47 carried bychanneled beam 41. Rack 47 is of adequate length so that uponappropriate operation of motor 45, the ejector-reverser barrel 20 istranslated along its support rails between the respective stowed anddeployed positions of FIGS. 4 and 5, or selectively to any intermediateposition therebetween.

Shield has a pair of support rails of which one of the rails 48 bestappears in FIG. 6. Rail 48 has a cross-sectional portion which isdovetailed in shape so as to be slidably received in the outer channel43 of beam 41, its diametrically opposed counterpart rail beingsimilarly received in the channeled beam on the other side of theejectonreverser barrel 20'. These support rails for shield 10' extendalong the longitudinal edge portions of the shield and are securedthereto so that the shield is translatable between its stowed positionon barrel 20', as shown in FIG. 4, and its deployed position downstreamof the barrel, as shown in FIG. 5, as the support rails are movedslidably along their channeled beams.

A suitable actuator motor 51 is mounted as by the bracket 52 to thechanneled beam 41, and its actuator screw 53, or the like, is secured asby the bracket 54 to rail 48 at its trailing end so that the shield 10is moved between its stowed and deployed positions, or any intermediateposition on barrel 20, as desired, upon suitable operation of theactuator motor 51.

With the parts in the full line deployed position of FIG. 5, theaircraft is in the takeoff mode, and the ejector-reverser barrel 20'serves as a highly effective ejector to substantially enhance the thrustof the engine 12 during takeoff. To this end, the contour of the ejectorbarrel is designed to give optimum ejector performance. Referring toFIG. 7 it will be seen that the leading inner surface 55 of ring 21 andits adjacent reverser door 25' converges at an angle of about 5% to athroat 56 after which the inner barrel surface 57 diverges at about 4tothe downstream end of the barrel. The stangs also have thisconvergent-divergent barrel inner wall configuration. Surface 55 is cutaway in the region of each of the reverser doors, as depicted by thedashed line 58 of FIG. 7, to form the end plate configuration 29'required for effecting the forward directing of the jetstream when thereverser doors 24' and 25' are moved to their deployed position foreffecting thrust reversal, as depicted by the dashed lines in FIG. 5.

The cowling panel 10 for enclosing the engine 12 and/or the cowling 11may be removable to make the engine accessible for servicing as in thearrangement of FIGS. 1 to 3.

In the inflight position of the parts, as shown in FIG. 4, theejector-reverser barrel 20' serves as a fairing about the corrugatednozzle to reduce base drag, as aforedescribed in connection with theembodiment of FIGS. 1 to 3. It will be apparent, moreover, that thereflector/suppressor apparatus of FIGS. 4 to 7, in addition to itsoperative modes disclosed in FIG. 4 and 5, may by virtue of thetranslational movements of barrel 20 and shield 10' and the nature ofthe drives 45 and 51 for these members, that the same may haveadditional operative modes. Thus for example, the barrel 20 may beextended without extending the shield 10 to thus produce thrustaugmentation without the sound suppression afforded by the shield 10'.This arrangement is useful in the case of an abortive landing in whichthe reverser doors have been deployed but the aircraft cannot be broughtto a stop and must takeoff again. In such case, withdrawal of thereverser doors to stowed position on the barrel 20', restores the barrelto its takeoff position. On the other hand, in the case of an abortivetakeoff, the barrel 20' and the shield 10 being deployed, the reverserdoors may also be deployed to stop the aircraft.

Shield 10', furthermore, may be extended without extending the barrel20' to thus provide a sound suppressor arrangement similar to that ofFIGS. 1 to 3, but with half the length of shield 10. In addition, boththe barrel 20' and the shield 10' may be extended variously, that is,their condition of downstream extension may be modulated, eithertogether or separately, to vary the effective combined length of thesemembers as well as the effective lengths of each separately relative tothe exit plane of nozzle 15. It will be apparent, moreover, that suchmodulation of the members 10 and 20' could be accomplished automaticallyunder control of sensors responsive to varying operating conditions,such sensors being appropriately deployed to measure such factors asaircraft speed, thrust, jet velocity, temperature, and divergence angle,and other conditions affecting thrust and noise generation.

Whereas in the foregoing specific embodiments and arrangements of theinvention have been disclosed and described, it will be understood thatvarious modifications and different arrangements of the parts may bemade without departing from the spirit and scope of the invention.

What is claimed and desired to be secured by Letters Patent of theUnited States is:

I. The method of suppressing the noise of an aircraft having a jetengine which comprises:

the step preparatory to takeoff of the aircraft of extending areflector/suppressor shield to a deployed position sufficientlydownstream of the engine nozzle to intercept the cone of noiseaccompanying the jet stream several nozzle diameters aft of the nozzlein the region of the expansion boundary of the jet stream where thenoise level is maximum so that such noise which otherwise would beradiated toward the ground is reflected by the reflector/suppressorshield, thereby to reduce substantially the effective perceived noiselevel at the ground during takeoff, and

the step of interposing an ejector barrel between the extendedreflector/suppressor shield and the end of the nozzle to provide soundsuppression and thrust augmentation by mixing of the ejector-entrainedair with the jet stream, and

the step after takeoff of withdrawing the reflector/suppressor shieldfrom its deployed position to a stowed position disposed about thenozzle axis and upstream of the end of the nozzle.

2. The method as in claim 1 wherein the reflector/suppressor shield isformed as a separable part of the engine housing and the steps ofextending and withdrawing the shield include the steps of translatingthe shield between said stowed and deployed positions thereof and in andout of the housing.

3. The method as in claim 2 including the step of removing thereflector/suppressor from the engine housing to expose an area of theengine for servicing.

4. The method as in claim 1 wherein the jet engine has thrust reverserdoors for braking of the aircraft on landing and the method includes thesteps of moving the doors between stowed and deployed positions thereofwherein the doors in the stowed position are arranged about the enginenozzle, and in the deployed position are extended substantiallytransversely of the nozzle axis and aft of the nozzle effectively toblock and reverse the direction of the jetstream issuing from thenozzle.

5. The method of suppressing the noise of an aircraft jet engine havingthrust reverser doors for braking of the aircraft on landing in themethod comprises:

the step preparatory to takeoff of the aircraft of extending areflector/suppressor shield to a deployed position suffcientlydownstream of the engine nozzle to intercept the cone of noiseaccompanying the jetstream several nozzle diameters aft of the nozzle inthe region of the expansion boundary of the jetstream where the noiselevel is maximum so that such noise which otherwise would be radiatedtoward the ground is reflected by the reflector/suppressor shield,thereby to reduce substantially the effective perceived noise level atthe ground during takeoff,

the step after takeofi' of withdrawing the reflector/suppressor shieldfrom its deployed position to a stowed position disposed about thenozzle axis and upstream of the end of the nozzle,

the steps of moving the doors between stowed and deployed positionsthereof wherein the doors in the stowed position are arranged about theengine nozzle, and in the deployed position are extended substantiallytransversely of the nozzle axis and aft of the nozzle effectively toblock and reverse the direction of the jetstream issuing from thenozzle,

said reverser doors in said stowed position thereof forming an ejectorbarrel about the end portion of the nozzle, and

the step of passing ejector-entrained slipstream air for mixing with thejetstream to effect sound suppression and thrust augmentation therebywhile said reflector/suppressor is in said deployed position thereofduring takeoff of the aircraft.

6. The method as in claim wherein the engine nozzle is corrugated andthe method includes the steps of dividing the jetstream issuing from thenozzle and dividing the air stream drawn into the ejector barrel by thedividing action of the corrugated surfaces internally and externally ofthe nozzle, thereby to promote mixing of the divided jet and air streamsin the deployed position of the reflector/suppressor during takeoff, andalso thereby to reduce base drag of the corrugated nozzle by reason ofthe air flow thereover during the inflight operation of the aircraft.

7. The method as in claim 1 and including the steps of translating theejector barrel between stowed and deployed positions thereof wherein theejector barrel in the stowed position is disposed around the end portionof the nozzle and in the deployed position is disposed downstream of thenozzle.

8. The method as in claim 7 and including the steps of movably mountingthe reflector/suppressor shield on the ejector barrel and translatingthe same between a stowed position on the ejector barrel and saiddeployed position extending downstream thereof.

9. The method as in claim 8 and including the steps of movably mountinga pair of thrust reverser doors on the ejector barrel and moving thedoors between stowed and deployed positions during the landing of theaircraft.

10. The method as in claim 9 and including the steps of translating theejector barrel and the reflector/suppressor shield to said deployedpositions thereof and moving the reverser doors to said deployedpositions thereof.

11. The method as in claim 10 including the steps of mounting thereverser doors as separable portions of the ejector barrel in the stowedposition of the doors and extending the doors in deployed positiontransversely of the jetstream axis and aft of the nozzle so that thejetstream is blocked and reversed thereby.

12. The method as in claim 1 wherein the end portion of the nozzle iscorrugated and wherein the method includes dividing the jetstream andentrained air by the corrugated internal and external surfaces of thenoule to promote said mixing of the jet and air streams, and also toreduce base drag when the ejector barrel is in the stowed positionthereof.

13. Apparatus for suppressing the noise of an aircraft having a jetengine, said apparatus comprising, in combination, a translatablereflector/suppressor shield which extends in a deployed position thereofinto the region of the expansion boundary of the jetstream issuing fromthe engine nozzle to intercept the accompanying cone of noise arisingseveral nozzle diameters downstream of the nozzle whereby such noisewhich otherwise would be radiated toward and reach the ground withobjectionable intensity during takeoff of the aircraft is reflectedupwardly by the shield thereby to reduce substantially the effectiveperceived noise level at the ground, and means for translating theshield between said deployed position and a stowed position wherein theshield is disposed about the axis of the nozzle and upstream of saidexpansion boundary of the jetstream, and an ejector barrel interposedbetween the extended shield and nozzle and comprising a part of saidmeans for translating said shield between said stowed and deployedpositions thereof.

14. Apparatus as in claim 13 wherein the shield is substantially ofsemicylindrical configuration and forms a separable part of the enginehousing in said stowed position of the shield whereby the engine isexposed for servicing when the shield is removed from the housing.

15. Apparatus as in claim 13 and further comprising a pair of thrustreverser doors movably mounted in stowed position about the end portionof the nozzle on diametrically opposite sides thereof, and, when saidshield is in the stowed position thereof, being movable to a deployedposition in which the doors extend substantially transversely of thenozzle axis and aft of the end of the nozzle so that the jetstreamissuing therefrom is blocked and effectively directed forwardly of theengine.

16. Apparatus as in claim 13 wherein said shield is substantially ofsemicylindrical configuration and substantially of same length as saidejector barrel, said apparatus further comprising means for movablymounting the shield on said ejector barrel for translational movementaxially thereof, and means on the ejector barrel for moving said shieldtranslationally of the ejector barrel to said deployed position of theshield.

17. Apparatus as in claim 16 wherein said ejector barrel is translatablefrom a stowed position surrounding an end portion of the nozzle to saidinterposed position thereof between the nozzle and shield, and whereinsaid apparatus further comprises means for translating said ejectorbetween said stowed and interposed positions thereof.

18. Apparatus as in claim 16 wherein said ejector barrel has a pair ofthrust reverser doors separably formed therewith and movable in saidinterposed position of the ejector to a deployed position extendingsubstantially transversely of the jetstream axis and aft of the end ofthe nozzle so that the jetstream is effectively blocked by the doors insaid deployed position thereof and directed forwardly of the engine.

19. Apparatus as in claim 17 wherein said end portion of the nozzle iscorrugated to cause division of the issuing jetstream and of the airstream drawn into the ejector barrel when said doors are closed, saidejector barrel when in said stowed position thereof also reducing basedrag by the air drawn therethrough and passed over the external surfaceof the corrugated nozzle.

20. Apparatus as in claim 18, said ejector barrel having innerconvergent-divergent surfaces, and the convergent surface portions ofsaid doors having end plate configurations to effect said forwarddirecting of the jetstream.

21. Apparatus for suppressing the noise of an aircraft having a jetengine, said apparatus comprising, in combination, a translatablereflector/suppressor shield which extends in a deployed position thereofinto the region of the expansion boundary of the jetstream issuing fromthe engine nozzle to intercept the accompanying cone of noise arisingseveral nozzle diameters downstream of the nozzle whereby such noisewhich otherwise would be radiated toward and reach the ground withobjectionable intensity during takeoff of the aircraft is reflectedupwardly by the shield thereby to reduce substantially the effectiveperceived noise level at the ground, means for translating the shieldbetween said deployed position and a stowed position wherein the shieldis disposed about the axis of the nozzle and upstream of said expansionboundary of the jetstream stream, a pair of thrust reverser doorsmovably mounted in stowed position about the end portion of the nozzleon diametrically opposite sides thereof and, when said shield is in thestowed position thereof, being movable to a deployed position in whichthe doors extend substantially transversely of the nozzle axis and aftof the end of the nozzle so that the jet stream issuing therefrom isblocked and effectively directed forwardly of the engine, and saidreverser doors in the stowed position thereof forming an ejector barrelaround said end portion of the nozzle, thereby to entrain slipstream airfor mixing with the jetstream to provide sound suppression and thrustaugmentation during takeoff.

22. Apparatus as in claim 17 wherein said end portion of the nozzle iscorrugated to divide said jet stream and said entrained air, thereby topromote mixing of said divided jet and air streams during takeoff, andalso to reduce base drag of the corrugated nozzle during the inflightoperation of the aircraft.

1. The method of suppressing the noise of an aircraft having a jetengine which comprises: the step preparatory to takeoff of the aircraftof extending a reflector/suppressor shield to a deployed positionsufficiently downstream of the engine nozzle to intercept the cone ofnoise accompanying the jet stream several nozzle diameters aft of thenozzle in the region of the expansion boundary of the jet stream wherethe noise level is maximum so that such noise which otherwise would beradiated toward the ground is reflected by the reflector/suppressorshield, thereby to reduce substantially the effective perceived noiselevel at the ground during takeoff, and the step of interposing anejector barrel between the extended reflector/suppressor shield and theend of the nozzle to provide sound suppression and thrust augmentationby mixing of the ejector-entrained air with the jet stream, and the stepafter takeoff of withdrawing the reflector/suppressor shield from itsdeployed position to a stowed position disposed about the nozzle axisand upstream of the end of the nozzle.
 2. The method as in claim 1wherein the reflector/suppressor shield is formed as a separable part ofthe engine housing and the steps of extending and withdrawing the shieldinclude the steps of translating the shield between said stowed anddeployed positions thereof and in and out of the housing.
 3. The methodas in claim 2 including the step of removing the reflector/suppressorfrom the engine housing to expose an area of the engine for servicing.4. The method as in claim 1 wherein the jet engine has thrust reverserdoors for braking of the aircraft on landing and the method includes thesteps of moving the doors between stowed and deployed positions thereofwherein the doors in the stowed position are arranged about the enginenozzle, and in the deployed position are extended substantiallytransversely of the nozzle axis and aft of the nozzle effectively toblock and reverse the direction of the jetstream issuing from thenozzle.
 5. The method of suppressing the noise of an aircraft jet enginehaving thrust reverser doors for braking of the aircraft on landing inthe method comprises: the step preparatory to takeoff of the aircraft ofextending a reflector/suppressor shield to a deployed positionsufficiently downstream of the engine nozzle to intercept the cone ofnoise accompanying the jetstream several nozzle diameters aft of thenozzle in the region of the expansion boundary of the jetstream wherethe noise level is maxiMum so that such noise which otherwise would beradiated toward the ground is reflected by the reflector/suppressorshield, thereby to reduce substantially the effective perceived noiselevel at the ground during takeoff, the step after takeoff ofwithdrawing the reflector/suppressor shield from its deployed positionto a stowed position disposed about the nozzle axis and upstream of theend of the nozzle, the steps of moving the doors between stowed anddeployed positions thereof wherein the doors in the stowed position arearranged about the engine nozzle, and in the deployed position areextended substantially transversely of the nozzle axis and aft of thenozzle effectively to block and reverse the direction of the jetstreamissuing from the nozzle, said reverser doors in said stowed positionthereof forming an ejector barrel about the end portion of the nozzle,and the step of passing ejector-entrained slipstream air for mixing withthe jetstream to effect sound suppression and thrust augmentationthereby while said reflector/suppressor is in said deployed positionthereof during takeoff of the aircraft.
 6. The method as in claim 5wherein the engine nozzle is corrugated and the method includes thesteps of dividing the jetstream issuing from the nozzle and dividing theair stream drawn into the ejector barrel by the dividing action of thecorrugated surfaces internally and externally of the nozzle, thereby topromote mixing of the divided jet and air streams in the deployedposition of the reflector/suppressor during takeoff, and also thereby toreduce base drag of the corrugated nozzle by reason of the air flowthereover during the inflight operation of the aircraft.
 7. The methodas in claim 1 and including the steps of translating the ejector barrelbetween stowed and deployed positions thereof wherein the ejector barrelin the stowed position is disposed around the end portion of the nozzleand in the deployed position is disposed downstream of the nozzle. 8.The method as in claim 7 and including the steps of movably mounting thereflector/suppressor shield on the ejector barrel and translating thesame between a stowed position on the ejector barrel and said deployedposition extending downstream thereof.
 9. The method as in claim 8 andincluding the steps of movably mounting a pair of thrust reverser doorson the ejector barrel and moving the doors between stowed and deployedpositions during the landing of the aircraft.
 10. The method as in claim9 and including the steps of translating the ejector barrel and thereflector/suppressor shield to said deployed positions thereof andmoving the reverser doors to said deployed positions thereof.
 11. Themethod as in claim 10 including the steps of mounting the reverser doorsas separable portions of the ejector barrel in the stowed position ofthe doors and extending the doors in deployed position transversely ofthe jetstream axis and aft of the nozzle so that the jetstream isblocked and reversed thereby.
 12. The method as in claim 1 wherein theend portion of the nozzle is corrugated and wherein the method includesdividing the jetstream and entrained air by the corrugated internal andexternal surfaces of the nozzle to promote said mixing of the jet andair streams, and also to reduce base drag when the ejector barrel is inthe stowed position thereof.
 13. Apparatus for suppressing the noise ofan aircraft having a jet engine, said apparatus comprising, incombination, a translatable reflector/suppressor shield which extends ina deployed position thereof into the region of the expansion boundary ofthe jetstream issuing from the engine nozzle to intercept theaccompanying cone of noise arising several nozzle diameters downstreamof the nozzle whereby such noise which otherwise would be radiatedtoward and reach the ground with objectionable intensity during takeoffof the aircraft is reflected upwardly by the shield thereby to reducesubstantially the effective perceivEd noise level at the ground, andmeans for translating the shield between said deployed position and astowed position wherein the shield is disposed about the axis of thenozzle and upstream of said expansion boundary of the jetstream, and anejector barrel interposed between the extended shield and nozzle andcomprising a part of said means for translating said shield between saidstowed and deployed positions thereof.
 14. Apparatus as in claim 13wherein the shield is substantially of semicylindrical configuration andforms a separable part of the engine housing in said stowed position ofthe shield whereby the engine is exposed for servicing when the shieldis removed from the housing.
 15. Apparatus as in claim 13 and furthercomprising a pair of thrust reverser doors movably mounted in stowedposition about the end portion of the nozzle on diametrically oppositesides thereof, and, when said shield is in the stowed position thereof,being movable to a deployed position in which the doors extendsubstantially transversely of the nozzle axis and aft of the end of thenozzle so that the jetstream issuing therefrom is blocked andeffectively directed forwardly of the engine.
 16. Apparatus as in claim13 wherein said shield is substantially of semicylindrical configurationand substantially of same length as said ejector barrel, said apparatusfurther comprising means for movably mounting the shield on said ejectorbarrel for translational movement axially thereof, and means on theejector barrel for moving said shield translationally of the ejectorbarrel to said deployed position of the shield.
 17. Apparatus as inclaim 16 wherein said ejector barrel is translatable from a stowedposition surrounding an end portion of the nozzle to said interposedposition thereof between the nozzle and shield, and wherein saidapparatus further comprises means for translating said ejector betweensaid stowed and interposed positions thereof.
 18. Apparatus as in claim16 wherein said ejector barrel has a pair of thrust reverser doorsseparably formed therewith and movable in said interposed position ofthe ejector to a deployed position extending substantially transverselyof the jetstream axis and aft of the end of the nozzle so that thejetstream is effectively blocked by the doors in said deployed positionthereof and directed forwardly of the engine.
 19. Apparatus as in claim17 wherein said end portion of the nozzle is corrugated to causedivision of the issuing jetstream and of the air stream drawn into theejector barrel when said doors are closed, said ejector barrel when insaid stowed position thereof also reducing base drag by the air drawntherethrough and passed over the external surface of the corrugatednozzle.
 20. Apparatus as in claim 18, said ejector barrel having innerconvergent-divergent surfaces, and the convergent surface portions ofsaid doors having end plate configurations to effect said forwarddirecting of the jetstream.
 21. Apparatus for suppressing the noise ofan aircraft having a jet engine, said apparatus comprising, incombination, a translatable reflector/suppressor shield which extends ina deployed position thereof into the region of the expansion boundary ofthe jetstream issuing from the engine nozzle to intercept theaccompanying cone of noise arising several nozzle diameters downstreamof the nozzle whereby such noise which otherwise would be radiatedtoward and reach the ground with objectionable intensity during takeoffof the aircraft is reflected upwardly by the shield thereby to reducesubstantially the effective perceived noise level at the ground, meansfor translating the shield between said deployed position and a stowedposition wherein the shield is disposed about the axis of the nozzle andupstream of said expansion boundary of the jetstream stream, a pair ofthrust reverser doors movably mounted in stowed position about the endportion of the nozzle on diametrically opposite sides thereof and, whensaid sHield is in the stowed position thereof, being movable to adeployed position in which the doors extend substantially transverselyof the nozzle axis and aft of the end of the nozzle so that the jetstream issuing therefrom is blocked and effectively directed forwardlyof the engine, and said reverser doors in the stowed position thereofforming an ejector barrel around said end portion of the nozzle, therebyto entrain slipstream air for mixing with the jetstream to provide soundsuppression and thrust augmentation during takeoff.
 22. Apparatus as inclaim 17 wherein said end portion of the nozzle is corrugated to dividesaid jet stream and said entrained air, thereby to promote mixing ofsaid divided jet and air streams during takeoff, and also to reduce basedrag of the corrugated nozzle during the inflight operation of theaircraft.